Method and system for localisation on a dc lighting and power grid

ABSTRACT

The present disclosure is directed to methods and apparatus for locating luminaires within a lighting system where multiple luminaires are located on a grid of DC power rails. The AC signal generator connects to each DC power rail and transmits an AC signal along each DC power rail in turn to luminaires that each compute their distance from the generator based upon the AC signal. The AC signal generator may similarly transmit and receive data communications with luminaires across DC power rails.

TECHNICAL FIELD

The present invention is directed generally to illumination systems.More particularly, various inventive methods and apparatus disclosedherein relate to lighting and power distribution systems.

BACKGROUND

Digital lighting technologies, i.e. illumination based on semiconductorlight sources, such as light-emitting diodes (LEDs), offer a viablealternative to traditional fluorescent, HID, and incandescent lamps.Functional advantages and benefits of LEDs include high energyconversion and optical efficiency, durability, lower operating costs,and many others. Recent advances in LED technology have providedefficient and robust full-spectrum lighting sources that enable avariety of lighting effects in many applications.

Traditional lighting installations, particularly in office spaces andother similar environments, have typically adopted a simplepoint-to-point connection methodology, where power is supplied to eachluminaire via a dedicated, but essentially “free floating”, power cable.These power cables, which, in many regions, carry a high AC voltage, forexample, 240V, typically hop from luminaire to luminaire, in a generallyad hoc manner, until all lamps are included in the system. In addition,each luminaire often requires the installation of a separate switchcable that connects each lamp or fitting to a dedicated control switchor bank of switches.

In a typical office lighting installation, luminaires are usually placedin a rectangular grid pattern, however, the cable routing above theceiling, needed to supply these luminaire grids are by contrast veryoften quite irregular in their placement. In many cases the placementand routing of the power cables is left to the discretion of individualinstallers.

To help address this situation, a standard is being developed within analliance called “EMerge,” an open industry association developingstandards leading to the rapid adoption of DC power distribution incommercial buildings. The EMerge standard proposes the use of safe, lowvoltage (24V dc) power distribution and a more structured power supplyscheme based on the use of rigid bus bars running above the ceiling.This system facilitates simplified and safe removal, connection, orre-location of lights in a lighting system. Also, because the bus barsystem can be organized in a grid structure above the ceiling, it may bemore suitable for connection with a luminaire grid that it providespower to. An example of a section of the proposed EMerge power supplybus bar, and the connectors needed to supply power to individualluminaires, and other devices in an office ceiling, are shown in FIG. 1.

Since the EMerge standard has been designed to make it easier for usersto move and reconfigure lighting installations on-the-fly, it isdesirable to ensure that luminaires can be easily associated anddisassociated with control switches. To that end, EMerge proposes theuse of wireless communications systems (currently ZigBee), rather thanphysical wires, to connect luminaires with user operated control points,for example, wall switches.

While traditional point-to-point style wiring strategies have verylittle impact on day-to-day use of office lighting installations, theypresent significant drawbacks regarding installing and commissioninglighting systems. Further, the point-to-point cabling used for aninitial system may not be suitable for future modifications.

A major difficulty with commissioning any new lighting system is how toaccurately map luminaires with control units or switches. For example,routing the wiring between a particular switch on the wall to theluminaire it controls in the ceiling. Traditionally the wholecommissioning process is completely manual. The installer needs to firstassociate luminaires in the ceiling with luminaires indicated in alighting plan and ensure that said luminaire is hard wired to whicheverswitch has also been indicated on the plan as being the control pointfor that lamp. In the case of traditionally wired systems this processis slow and laborious. Situations become more difficult when it becomesdesirable to control traditionally wired luminaries by wireless means.In this case it becomes necessary for the installation engineer torecord the unique wireless identifier (ID number) associated with eachluminaire and to transfer that information to the lighting plan. Whenwireless lighting controls, such as switches, are then installed, itsimilarly becomes necessary to transfer the switch ID details to thelighting plan. The next step in the process is typically to manuallycreate a binding table somewhere in the control system to associateswitches with luminaires. Finally, the system needs to be tested toensure that the desired binding have been allocated correctly.

Therefore, it is desirable to simplify the controller-luminaire mappingprocess. For example, the luminaire and control point mapping processcould be automated, if the physical location of every luminaire in theceiling was provided to the system.

Currently, many conventional technical solutions for locating objectsemploy wireless technologies, such as ZigBee or WiFi. Within thisgeneral category of solutions, the two most common systems to be foundare either signal strength based or time of flight based.

Radio location systems that use signal strength as the basis for theirmeasurement, for example those produced by AeroScout and Ekahau, aregenerally relatively easy to implement at modest cost, but have ratherpoor intrinsic accuracy, varying by perhaps five meters from of the truelocation. Accuracy can be improved with a technique known as fingerprinting, which involves measuring the signal strength at every point ina room in advance. However, the process is laborious to carry out andthe resulting finger print profile may change with minor alterationswithin the room, for example moving furniture.

Location systems based on time of flight, such as those, for example,developed by UbiSense of Cambridge, United Kingdom, can achieve muchgreater accuracy than signal strength based alternatives, however, theyare complex and expensive to implement, and can still suffer fromaccuracy or reliability problems due to propagation effects such asmultipath or fading. EMerge supports wireless communication with eachluminaire on the DC grid. Such communication may be used to controlfunctions of each luminaire, for example, on/off state, intensity andcolor selection. However, it may be costly and cumbersome to equip eachluminaire with a wireless transceiver and to configure wirelesscommunication with each luminaire.

Thus, there is a need in the art to simply and cost effectively obtainand monitor the location of luminaires in a lighting system. Furtherthere is a need for simpler and more cost effective controlcommunication with luminaires in a lighting system.

SUMMARY

The present disclosure is directed to inventive methods and apparatusfor locating luminaires within a lighting system. For example,embodiments of the present invention relate to systems and methods wheremultiple luminaires are located on a grid of DC power rails. A single ACsignal generator may work in concert with a multiplexer that selectseach DC power rail in round-robin fashion. The AC signal generatortransmits an AC signal along each DC power rail in turn to luminairesthat each computes their distance from the generator based upon the ACsignal. Specific embodiments correspond to signal types that may be usedfor the luminaire to calculate the distance between the generator andthe luminaire. Each luminaire may include AC signal receiver circuitry,logic circuitry capable of calculating the distance based on thereceived signal, memory to store the calculated distance, and a meansfor transmitting that distance to a room controller. Each luminaire maycalculate and store the distance and then communicate that distance to aroom controller or similar device. These embodiments leverage existingpower infrastructure and layout to add location and communicationfeatures with high precision and relatively low additional cost andcomplexity.

In addition, the AC signal generator may transmit and receive datacommunications with luminaires across DC power rails. Such datacommunications may be used in place of, or in concert with, other datacommunications channels between individual luminaires and an internal orexternal controller.

Generally, in a first aspect, a method for locating a luminaire on a DCgrid includes a first DC grid power line, an AC signal generatorswitchably connected to the first DC grid power line, and a firstluminaire in electrical communication with the first DC grid power line.The first luminaire is disposed along the first DC grid power line at afirst distance from the AC signal generator. The method includes thesteps of connecting the AC signal generator to the first DC grid powerline, transmitting, by the AC signal generator, an AC signal along thefirst DC grid power line, receiving the AC signal by the firstluminaire, and calculating the first distance between the AC signalgenerator and the first luminaire, based in part upon the AC signal.

In a first embodiment, the first DC grid power line is terminated forthe AC signal with a resistance approximating a characteristic impedanceof the first DC grid power line. Under the first embodiment, the methodfurther includes the steps of recording, by the first luminaire, a firstphase of the AC signal at the first luminaire, and recording, by the ACsignal generator, a second phase of the AC signal at the AC signalgenerator. The step of calculating the first distance further includesmeasuring a difference between the first phase and the second phase.

In a second embodiment, the first DC grid power line is unterminated forthe AC signal. The method includes the steps of setting the frequency ofthe AC signal such that the AC signal forms a standing wave across thefirst DC grid power line, the standing wave including a maximumamplitude, and recording, by the first luminaire, a first amplitude ofthe AC signal at the first luminaire. The step of calculating the firstdistance further includes measuring a difference between the firstamplitude and the maximum amplitude.

In a third embodiment under the first aspect, the first DC grid powerline is unterminated for the AC signal, and the AC signal has anamplitude. The method of the first aspect further includes the steps ofsweeping the frequency of the AC signal between a first frequency and asecond frequency, recording, by the first luminaire, a first timecorresponding to a time the first luminaire initially detects the ACsignal, and recording, by the first luminaire, a second timecorresponding to a time the first luminaire detects the amplitude of theAC signal corresponding to a null amplitude. The step of calculating thefirst distance further includes measuring a difference between the firsttime and the second time.

In a fourth embodiment under the first aspect, the AC signal is a pulsesignal, and the first DC grid power line is unterminated for the ACsignal. The method further includes the steps of recording, by the firstluminaire, a first time corresponding to a time the first luminaireinitially detects the pulse signal, and recording, by the firstluminaire, a second time corresponding to a time the first luminaireinitially detects a reflection of the pulse signal. The step ofcalculating the first distance further includes measuring a differencebetween the first time and the second time.

Under a first version of the first aspect, the DC grid further has asecond DC grid power line, the AC signal generator switchably connectedto the second DC grid power line, and a second luminaire in electricalcommunication with the second DC grid power line. The second luminaireis disposed along the second DC grid power line at a second distancefrom the AC signal generator. The method includes the steps ofconnecting the AC signal generator to the second DC grid power line,transmitting, by the AC signal generator, an AC signal along the secondDC grid power line, receiving the AC signal by the second luminaire, andcalculating the second distance between the AC signal generator and thesecond luminaire, based in part upon the AC signal.

Under a second version of the first aspect, the DC grid includes amemory element. The method further includes the steps of storing thefirst distance in the memory and communicating the first distance to aDC grid mapper. The step of communicating the first distance to the DCgrid mapper may include transmitting a wireless signal to the DC gridmapper. The memory may optionally be disposed within the firstluminaire, where the DC grid mapper is in electrical communication withthe DC grid. The step of communicating the first distance to a DC gridmapper may include the step of transmitting a communication signal alongthe first DC grid power line from the first luminaire to the DC gridmapper.

Generally, in a second aspect, the invention relates to a system thatincludes a DC power grid including a plurality of DC power lines, withan AC signal generator switchably connected to at least one of theplurality of DC grid power lines. The AC signal generator is configuredto transmit a locator signal along at least one of the plurality of DCgrid power lines. A plurality of luminaires is disposed upon the DCpower grid. Each of the luminaires includes a receiver configured toreceive the locator signal, logic circuitry configured to calculate adistance between the luminaire and the AC signal generator based on thelocator signal, memory configured to store the distance, and means fortransmitting the distance to a room controller. Under one embodiment,the DC grid is an Emerge compliant lighting system.

Under a second embodiment, the AC signal generator is configured totransmit the locator signal within a first frequency band and furtherconfigured to transmit and receive data within a second frequency band.17. The plurality of luminaires are configured to receive the locatorsignal within the first frequency band and further configured to receivedata within the second frequency band. The locator signal may optionallybe a standing wave or a pulse.

Generally, a third aspect of the invention relates to a method havingthe steps of providing a DC power grid including a plurality of DC powerlines and a plurality of luminaires disposed upon the plurality of DCpower lines, selecting a first luminaire from the plurality ofluminaires, assigning an ID to the first luminaire, associating thefirst luminaire with a first DC power line, storing a first coordinateindex including the association between the first luminaire and thefirst DC power line, calculating a position of the first luminaire inrelation to the first DC power line, storing a second coordinate indexincluding the position of the first luminaire in relation to the firstDC power line, and communicating the ID, the first coordinate index andthe second coordinate index to a room controller.

Generally, a fourth aspect is a method for controlling a first luminairein electrical communication with a first DC grid power line on a DCgrid. The first luminaire includes a first luminaire data transceiver.The DC grid includes the first DC grid power line, a grid datatransceiver switchably connected to the first DC grid power line, andthe first luminaire. The method includes the steps of connecting thegrid data transceiver to the first DC grid power line, transmitting, bythe grid data transceiver, a first data signal along the first DC gridpower line, receiving the first data signal by the first luminaire datatransceiver.

In a first embodiment under the fourth aspect, the DC grid furtherincluding the steps of transmitting, by the first luminaire datatransceiver, a second data signal along the first DC grid power line,and receiving the second data signal by the grid data transceiver.

In a second embodiment of the fourth aspect, the DC grid furtherincludes a second DC grid power line, and a second luminaire inelectrical communication with the second DC grid power line. The secondluminaire includes a second luminaire data transceiver. The grid datatransceiver is switchably connected to the second DC grid power line.The method further includes the steps of connecting the grid datatransceiver to the second DC grid power line, transmitting, by the griddata transceiver, a third data signal along the second DC grid powerline, and receiving the third data signal by the second luminaire datatransceiver.

As used herein for purposes of the present disclosure, the term “LED”should be understood to include any electroluminescent diode or othertype of carrier injection/junction-based system that is capable ofgenerating radiation in response to an electric signal. Thus, the termLED includes, but is not limited to, various semiconductor-basedstructures that emit light in response to current, light emittingpolymers, organic light emitting diodes (OLEDs), electroluminescentstrips, and the like. In particular, the term LED refers to lightemitting diodes of all types (including semi-conductor and organic lightemitting diodes) that may be configured to generate radiation in one ormore of the infrared spectrum, ultraviolet spectrum, and variousportions of the visible spectrum (generally including radiationwavelengths from approximately 400 nanometers to approximately 700nanometers). Some examples of LEDs include, but are not limited to,various types of infrared LEDs, ultraviolet LEDs, red LEDs, blue LEDs,green LEDs, yellow LEDs, amber LEDs, orange LEDs, and white LEDs(discussed further below). It also should be appreciated that LEDs maybe configured and/or controlled to generate radiation having variousbandwidths (e.g., full widths at half maximum, or FWHM) for a givenspectrum (e.g., narrow bandwidth, broad bandwidth), and a variety ofdominant wavelengths within a given general color categorization.

The term “light source” should be understood to refer to any one or moreof a variety of radiation sources, including, but not limited to,LED-based sources (including one or more LEDs as defined above),incandescent sources (e.g., filament lamps, halogen lamps), fluorescentsources, phosphorescent sources, high-intensity discharge sources (e.g.,sodium vapor, mercury vapor, and metal halide lamps), lasers, othertypes of electroluminescent sources, pyro-luminescent sources (e.g.,flames), candle-luminescent sources (e.g., gas mantles, carbon arcradiation sources), photo-luminescent sources (e.g., gaseous dischargesources), cathode luminescent sources using electronic satiation,galvano-luminescent sources, crystallo-luminescent sources,kine-luminescent sources, thermo-luminescent sources, triboluminescentsources, sonoluminescent sources, radioluminescent sources, andluminescent polymers.

The term “lighting fixture” or “luminaire” is used herein to refer to animplementation or arrangement of one or more lighting units in aparticular form factor, assembly, or package. The term “lighting unit”is used herein to refer to an apparatus including one or more lightsources of same or different types. A given lighting unit may have anyone of a variety of mounting arrangements for the light source(s),enclosure/housing arrangements and shapes, and/or electrical andmechanical connection configurations. Additionally, a given lightingunit optionally may be associated with (e.g., include, be coupled toand/or packaged together with) various other components (e.g., controlcircuitry) relating to the operation of the light source(s). An“LED-based lighting unit” refers to a lighting unit that includes one ormore LED-based light sources as discussed above, alone or in combinationwith other non LED-based light sources.

The term “controller” is used herein generally to describe variousapparatus relating to the operation of one or more light sources. Acontroller can be implemented in numerous ways (e.g., such as withdedicated hardware) to perform various functions discussed herein. A“processor” is one example of a controller which employs one or moremicroprocessors that may be programmed using software (e.g., microcode)to perform various functions discussed herein. A controller may beimplemented with or without employing a processor, and also may beimplemented as a combination of dedicated hardware to perform somefunctions and a processor (e.g., one or more programmed microprocessorsand associated circuitry) to perform other functions. Examples ofcontroller components that may be employed in various embodiments of thepresent disclosure include, but are not limited to, conventionalmicroprocessors, application specific integrated circuits (ASICs), andfield-programmable gate arrays (FPGAs).

The term “addressable” is used herein to refer to a device (e.g., alight source in general, a lighting unit or fixture, a controller orprocessor associated with one or more light sources or lighting units,other non-lighting related devices, etc.) that is configured to receiveinformation (e.g., data) intended for multiple devices, includingitself, and to selectively respond to particular information intendedfor it. The term “addressable” often is used in connection with anetworked environment (or a “network,” discussed further below), inwhich multiple devices are coupled together via some communicationsmedium or media.

In one network implementation, one or more devices coupled to a networkmay serve as a controller for one or more other devices coupled to thenetwork (e.g., in a master/slave relationship). In anotherimplementation, a networked environment may include one or morededicated controllers that are configured to control one or more of thedevices coupled to the network. Generally, multiple devices coupled tothe network each may have access to data that is present on thecommunications medium or media; however, a given device may be“addressable” in that it is configured to selectively exchange data with(i.e., receive data from and/or transmit data to) the network, based,for example, on one or more particular identifiers (e.g., “addresses”)assigned to it.

The term “network” as used herein refers to any interconnection of twoor more devices (including controllers or processors) that facilitatesthe transport of information (e.g. for device control, data storage,data exchange, etc.) between any two or more devices and/or amongmultiple devices coupled to the network. As should be readilyappreciated, various implementations of networks suitable forinterconnecting multiple devices may include any of a variety of networktopologies and employ any of a variety of communication protocols.Additionally, in various networks according to the present disclosure,any one connection between two devices may represent a dedicatedconnection between the two systems, or alternatively a non-dedicatedconnection. In addition to carrying information intended for the twodevices, such a non-dedicated connection may carry information notnecessarily intended for either of the two devices (e.g., an opennetwork connection). Furthermore, it should be readily appreciated thatvarious networks of devices as discussed herein may employ one or morewireless, wire/cable, and/or fiber optic links to facilitate informationtransport throughout the network.

It should be appreciated that all combinations of the foregoing conceptsand additional concepts discussed in greater detail below (provided suchconcepts are not mutually inconsistent) are contemplated as being partof the inventive subject matter disclosed herein. In particular, allcombinations of claimed subject matter appearing at the end of thisdisclosure are contemplated as being part of the inventive subjectmatter disclosed herein. It should also be appreciated that terminologyexplicitly employed herein that also may appear in any disclosureincorporated by reference should be accorded a meaning most consistentwith the particular concepts disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the sameparts throughout the different views. Also, the drawings are notnecessarily to scale, emphasis instead generally being placed uponillustrating the principles of the invention.

FIG. 1 illustrates an example implementation of an EMerge power bus barand connectors for supplying luminaires and peripherals.

FIG. 2A is a schematic diagram of an exemplary luminaire locationsystem.

FIG. 2B is a simple diagram of exemplary AC signaling and DC powerseparation circuitry.

FIG. 3 is a diagram detailing the physical transmission characteristicsof power bus bars under the Emerge standard.

FIG. 4 is a schematic diagram of exemplary AC signaling and DC powerseparation circuitry.

FIG. 5 is a flowchart of a first exemplary method for locating aluminaire on a DC power grid.

FIG. 6 is a flowchart of a first embodiment of a method for locating aluminaire on a DC power grid.

FIG. 7 is a schematic diagram of a first embodiment of a method forlocating a luminaire on a DC power grid.

FIG. 8 is a flowchart of a second embodiment of a method for locating aluminaire on a DC power grid.

FIG. 9 is a schematic diagram of a second embodiment of a method forlocating a luminaire on a DC power grid.

FIG. 10 is a flowchart of a third embodiment of a method for locating aluminaire on a DC power grid.

FIG. 11 is a schematic diagram of a third embodiment of a method forlocating a luminaire on a DC power grid.

FIG. 12 is a flowchart of a fourth embodiment of a method for locating aluminaire on a DC power grid.

FIG. 13 is a schematic diagram of a fourth embodiment of a method forlocating a luminaire on a DC power grid.

DETAILED DESCRIPTION

As mentioned above, there is a need to map the locations of luminairesdisposed within a lighting system, for example, luminaires incorporatedwithin an EMerge lighting grid. The approach described below aims tooffer an alternative method to address the luminaire location problem.

More generally, Applicants have recognized and appreciated that it wouldbe beneficial to provide more accurate luminaire location mapping thantime of flight based radio systems that are easier and less expensive toimplement than signal strength based systems. Also, since the inventionavoids the need to transmit radio signals to make ranging measurements,it may be less susceptible to changing propagation environments thatcharacterize many indoor locations.

In view of the foregoing, various embodiments and implementations of thepresent invention are directed to systems and methods for locatingluminaires within a DC power grid. While the invention as described heremakes use of the regular grid structure as proposed by the EMergespecification to locate luminaires in a lighting installation, theinvention is not limited to using the Emerge specification. For example,the invention is applicable in other systems where the position of thepower supply lines is known and the power supply lines are suitable forAC signal transmission.

DC Grid

A first exemplary embodiment of a DC grid, for example, as proposedwithin the EMerge standard, is shown in FIG. 2A. The DC grid includes anAC to DC converter 220, or transformer, for example, to convert theincoming high voltage (110V/240V) from an AC power supply 210 to lowvoltage (24V) DC as conveyed by a high voltage power line 215. Theoutput from the converter 220 is in turn connected to a series ofparallel bus bars, or grid lines 240, which together form the underlyinggrid structure of the lighting installation. Multiple luminaires 250 areconnected on grid lines 240 at arbitrary positions on each grid line240. As described below in this disclosure, the grid lines 240 of anEmerge system distribute power to the luminaires 250, and may also havethe electrical characteristics of transmission lines. For example, busbar configuration proposed in the EMerge standard include two parallelconductors separated over their entire length by insulating material ofrelatively narrow cross section.

The DC power may be distributed across the grid lines 240, for example,in parallel fashion. A multiplexer 230 may be used to connect acommunications transceiver 235, for example, a signal generator, to eachgrid line 240, so that the multiplexer 230 electrically connects thecommunications transceiver 235 to a selected grid line 240, or maydisconnect the communications transceiver 235 from the grid line 240. Aswill be explained further, the communications transceiver 235 may beused to transmit and/or receive location signals and/or datacommunications signals, for example, control messages, across the gridlines 240 to the luminaires 250. Such data communication signals may beconveyed to a room controller 260. The room controller 260 may include aDC grid mapper for determining and storing locations of luminaires 250in the lighting system, and may be located in close proximity orintegrated with the multiplexer 230, or may be external to themultiplexer 230.

FIG. 2B is a simplified diagram of a luminary 250 indicating circuitryfor separating DC power to the solid state luminaire (SSL) 252 from ACsignals that may be received by a transceiver 254.

Standard transmission line theory states that for a parallel conductingline of this type, the characteristic impedance (Z₀) is given by

$\begin{matrix}{Z_{0} = {\frac{1Z\; 0}{\sqrt{K}}{\ln \left( \frac{2S}{d} \right)}}} & {{Eq}.\mspace{14mu} 1}\end{matrix}$

where:K is the relative dielectric constant of the material between the twoconductorsS is the center-to-center separation of the two conductorsd is the diameter of the wires.

For example, referring to FIG. 3, the EMerge specification suggests fortypical bus bars, or rails, may have the following dimensions:

S=approximately 6.35 mm;D=approximately 4 mm;K=approximately 3.8 (for typical insulating material such asPolybutylene Terephthalate—PBT).

That means that Z₀ may be approximately 71Ω, which is close to typicalcoaxial cable Z₀ values of 50Ω/75Ω. Therefore, the DC power rails asspecified by the EMerge specification and other power distributionsystems may be suitable for transmitting AC signals, for example,location signals and/or data communication signals.

When high frequency signals are superimposed on the DC power voltage,for example, 24V, for luminaire localization or to convey controlsignals, power may be separated from localizing and/or control signalsin the luminaire. For example, this separation may be accomplished byinserting passive AC & DC blocks into the luminaire to allow DC power toreach the lamp and AC signaling frequencies to reach the internalcontrol logic, as shown in FIG. 2B.

FIG. 4 shows an exemplary embodiment of a power and signal separationcircuit 400 in more detail. An input 405 including DC power and locationand/or control signal is transported by a DC power conduit. A DC/ACfilter 410 separates the DC power from the AC location/control signal.The location/control signal is then amplified by a gain stage 420, andthen routed to mode detection circuitry 440 and band separationcircuitry 430. The band separation circuitry 430 may include a peakdetector 436, a low pass filter 434 and a first slicer 438. The outputof the first slicer 438 may contain a communications channel containingcontrol messaging, and is routed to a control module 474 in a processor470. The output of the low pass filter 434 may contain localizationsignals, and may be routed to a locator module 476 in the processor 470.

The mode detection circuitry 440 may be used to determine whether the AClocation/control signal is currently carrying a location signal or adata communications signal. The signal is processed by a band passfilter 444, a peak detector 446, and a second slicer 448, before beingrouted to a mode select block 478 in the processor 470. The mode selectblock 478 may indicate whether the signal is a locations signal or acommunications signal. Of course, a person skilled in the art willrecognize that other embodiment may be used to partition DC power, AClocation and AC communications signal within the scope of thisdisclosure.

In general, an exemplary method for localization of luminaires on a DCgrid may include two steps. The first step may determine which of themany parallel grid lines that the luminaire is located. For example,this may include determining a grid line number. The result from thefirst step above may be a digitized result where luminaires are locatedin integer grid positions. For example, in a first embodiment ofluminaires on a DC grid shown by FIG. 2A, three discrete DC power rails240 are depicted and six luminaires 250 are shown distributed amongthose power rails 250. If the grid numbering starts with top rail 240,three luminaires 250 are located on the top rail 240, two luminaires 250are on the middle rail 240, and a single luminaire 250 is on the bottomrail 240. For example, the top rail 240 may be designated as rail 1, thecenter rail 240 may be designated as rail 2, and the bottom rail 240 maybe designated as rail 3.

The second step may determine where on a given grid line a luminaire islocated. For example, the second step may entail determining how far aluminaire is located from the end of the grid line as determined in thefirst step. In addition the luminaire may store its position, and thenreport its position, for example, when queried by an externalcontroller.

The first step may be implemented by the following example. Themultiplexer 230 connects the AC signal transceiver 235 to a first rail240. A wake-up signal from the AC signal transceiver 235 to theluminaire 250 may contain coded information to identify a rail number ofthe rail 240 connecting the AC signal transceiver 235 to the luminaire250, for example to inform the luminaire 250 which rail 240 theluminaire 250 is connected to. Each luminaire 250 is woken up by thewake-up signal, and after a random back-off, each luminaire 250 maycommunicate a unique luminaire ID number to the AC signal transceiver235 connected to the multiplexer 230. The luminaire 250 may communicatethe luminaire ID to the AC signal transceiver 235 using, for example,Zigbee. The transceiver 235 receives the ID number of each respondingluminaire 250 and stores it in a luminaire table indexed by the railnumber. Each luminaire may decode the rail number that is encoded in thewake-up signal and store the grid number location locally in theluminaire 250. The multiplexer 230 then selects the next rail 240 insequence so the transceiver 235 may transmit the wake-up signal toluminaires 250 on the next rail 240. Note that while in the exampleabove the luminaire transmitted the luminaire ID across the rail, thereis no objection to the luminaire using other mechanisms to communicatethe luminaire ID to a luminaire table, for example, using a wirelesssignal.

After the multiplexer 230 has connected to each rail in turn, theluminaire table is available to the lighting system that describes whichluminaire 250 is associated with which rail 240. The luminaire table maythen be populated with localization information for each luminaire 250describing the distance along the rail between each luminaire 250 andthe AC signal transceiver 235, as described below.

Unlike step 1 above, the results of this location process of step 2 maybe continuous in nature in that a luminaire may be located at anyposition along a given power rail. To achieve a location determinationin this case involves treating each rail as a transmission line.Transmitting location signals of the appropriate waveform and frequencyalong the line and monitoring signals at luminaire attachment points maydetermine the location of a luminaire.

A generalized embodiment of a method for localization of luminaires on aDC grid is shown by a block diagram in FIG. 5. It should be noted thatany process descriptions or blocks in flow charts should be understoodas representing modules, segments, portions of code, or steps thatinclude one or more instructions for implementing specific logicalfunctions in the process, and alternative implementations are includedwithin the scope of the present invention in which functions may beexecuted out of order from that shown or discussed, includingsubstantially concurrently or in reverse order, depending on thefunctionality involved, as would be understood by those reasonablyskilled in the art of the present invention.

For exemplary purposes, the localization method shown in FIG. 5 makesreference to the grid system shown by FIG. 2A. The multiplexer 230 (FIG.2A) at one end of each rail 240 (FIG. 2A). The multiplexer 230 (FIG. 2A)may connect the AC signal transceiver 235 (FIG. 2A) to a rail 240 (FIG.2A), as shown by block 510. An AC locator signal may be transmittedacross the DC rail, as shown by block 520. Several embodiments of AClocator signals are described below. The AC locator signal is receivedby a luminaire, as shown by block 530. The luminaire analyzes the AClocator signal, as shown by block 540, to calculate the distance betweenthe luminaire and the AC signal transceiver, as shown by block 580.

Four specific embodiments of location methods using the generalizedembodiment described above are described below.

Embodiment 1 Phase Difference

FIG. 6 is a flowchart expanding and detailing block 540 of FIG. 5 for afirst embodiment of a luminaire location method. The first embodimentcalculates the distance of the luminaire from the AC signal generatorbased upon the differences in phase of a signal at different locationsalong the transmission line, or rail. Under the first embodiment, the ACsignal generator transmits a periodic wave, for example, a sine wave,across a DC power rail, as shown by block 520 (FIG. 5). A first phase ofthe AC signal is recorded at the luminaire, as shown by block 610. Asecond phase of the AC signal is recorded at the AC signal generator, asshown by block 620. A phase difference between the first phase and thesecond phase is calculated, as shown by block 630.

FIG. 7 illustrates an example of signals received at a first luminaire720 and a second luminaire 730 under the first embodiment, measuringphase differences. Here the grid line 750 is terminated in a resistance740 approximating the characteristic impedance of the line 750. A highfrequency signal 701 is then sent down the line 750. Because noreflections should theoretically be present, each position on the gridwill yield a sine wave whose phase angle increases relative to thedistance between the signal generator 710 and the luminaires 720, 730along the line 750.

The position along the line may be calculated by comparing phasedifferences. A first signal plot 711 represents the phase of the highfrequency signal 701 at the signal generator 710. Similarly, a secondsignal plot 721 represents the phase of the high frequency signal 701 atthe first luminaire 720, and a third signal plot 731 represents thephase of the high frequency signal 701 at the second luminaire 730.Since phase measurements are by their nature relative, the distancebetween the luminaires 720, 730 and the signal generator 710 may not beprecisely determined using phase differences alone. Therefore, it may benecessary to use the first embodiment technique in connection withanother technique or technology, for example, a coded light, toestablish a common timing between all the luminaires on the bus.

Embodiment 2 Amplitude Difference

FIG. 8 is a flowchart expanding and detailing block 540 of FIG. 5 for asecond embodiment of a luminaire location method. The second embodimentcalculates the distance of the luminaire from the AC signal generatorbased upon the differences in amplitude of a signal at differentlocations along the transmission line, or rail. Under the secondembodiment, the AC signal generator transmits a standing wave, forexample, a sine wave, across a DC power rail, as shown by block 810. Thefrequency of the AC signal is adjusted to create a standing wave havinga node at the signal generator. An amplitude of the AC signal isrecorded at the luminaire, as shown by block 820. A difference betweenthe first amplitude and the maximum amplitude is calculated, as shown byblock 830.

FIG. 9 illustrates an example of signals received at the first luminaire720 and the second luminaire 730 under the second embodiment, measuringamplitude differences across a standing wave. In this case the grid line750 is unterminated 940, that is, the circuit appears open to the highfrequency signal 901, such that the signal 901 is reflected at the endof the line causing standing waves across the transmission line 750. Ifthe frequency of the signal 901 at the signal generator 710 is adjustedto be a quarter wavelength, as shown, the amplitude of the signal 901increases from an amplitude of zero at the generator 710 to a maximumamplitude at the unterminated line end 940. The luminaires 720, 730store the maximum value of the signal 901 waveform that they detect, forexample by using an onboard ADC, and may report the amplitude after theinitial measurement period, for example, to a DC grid mapper or roomcontroller (not shown). Luminaire 720, 730 positions may be determinedby comparing the relative amplitudes.

While the signal 901 is represented as a quarter wavelength, there is noobjection to using other frequencies, for example, a half or eighthwavelength, or to taking subsequent measurements using differentwavelengths. This may assist in more accurately determining the positionof a luminaire positioned near the unterminated end. Similarly,subsequent measurements may be taken using a wavelength having a maximumamplitude at the signal generator 710 and a node at the unterminated end940. Under some embodiments, the AC signal generator may be adjustableto select a frequency appropriate to produce a standing wave accordingto the length of the rail. Once determined, the frequency may be storedby the AC generator for subsequent measurements.

Embodiment 3 Time to NULL (Frequency Sweep)

FIG. 10 is a flowchart expanding and detailing block 540 of FIG. 5 for athird embodiment of a luminaire location method. The third embodimentcalculates the distance of the luminaire from the AC signal generatorbased upon the frequency of signal where a node is detected along thetransmission line, or rail. Under the third embodiment, the AC signalgenerator transmits a swept frequency waveform, for example, a sinewave, across a DC power rail, as shown by block 520 (FIG. 5). Thefrequency of the AC signal is adjusted across a range, as shown by block1010, for example from a high frequency to a low frequency, or from alow frequency to a high frequency. The luminaire records a first time,corresponding to when the generator begins transmitting the sweptsignal, as shown by block 1020. The amplitude of the AC signal isdetected at the luminaire, and the time is recorded when the amplitudedetected at the luminaire is null, as shown by block 1030. A differencebetween the first amplitude and the maximum amplitude is calculated, asshown by block 1040.

When a high frequency signal is transmitted along an unterminatedtransmission line, an amplitude null occurs on the transmission line atlocations according to the length of the transmission line and thefrequency of the high frequency signal. If the length of thetransmission line is known, the position of an amplitude null on thetransmission line may be used to determine the distance of the null fromthe end of the transmission line. Therefore, if a null is detected at apoint along a transmission line, for example, a luminaire along a DCpower rail of known length, the distance of the luminaire from the endof the DC power rail may be determined.

FIG. 11 illustrates an example of signals received at the firstluminaire 720 and the second luminaire 730 under the third embodimentmeasuring the time difference between the initiation of a locationsignal and the detection of a null as the frequency of the signal isswept. The lines 750 are unterminated 940. The time taken at a luminaire720, 730 on the line 750 for the signal to decay to zero is a measure ofthe position of the luminaire 720, 730 from the end of the line 750. Theluminaires 720, 730 may store the result of the time measurement locallyand report it back to the infrastructure after the measurement, forexample, when the luminaire 720, 730 receives a measurement querymessage. The distance between the AC signal generator 710 and theluminaire 720, 730 may be calculated, for example, by determining thefrequency of the swept signal at the time the luminaire 720, 730reported a null amplitude.

As shown by the example in FIG. 11, The AC signal generator 710 maytransmit a first frequency 1011 at time t₁ and decrease the frequency ofthe AC signal at a constant rate. The first luminaire 720 may detect anull at a time t₂ corresponding to a second frequency 1121. The time t₂may be used to determine the second frequency 1121 the AC signalgenerator 710 was transmitting at time t₂, and thus the distance betweenthe first luminaire 720 and the AC signal generator 710 may bedetermined. Similarly, the second luminaire 730 may detect a null at atime t₃ corresponding to a third frequency 1131. The time t₃ may be usedto determine the third frequency 1131 the AC signal generator 710 wastransmitting at time t₃, and thus the distance between the secondluminaire 730 and the AC signal generator 710 may be determined.

It should be noted that while the above example the AC signal generator710 and the luminaires 720, 730 synchronize timing of the swept signalbased upon the time the swept signal starts, there is no objection toother methods of timing synchronization familiar to a person havingordinary skill in the art, so that the frequency 1121, 1131 of thesignal at the time a null is detected by a luminaire 720, 730 may bedetermined.

Embodiment 4 Pulse Spacing

FIG. 12 is a flowchart expanding and detailing block 540 of FIG. 5 for afourth embodiment of a luminaire location method. The fourth embodimentcalculates the distance of the luminaire from the AC signal generatorbased upon the propagation time of signal along the transmission line,or rail. Under the fourth embodiment, the AC signal generator configuresthe AC signal as a pulse, as shown by block 1210, for example, a unitstep function, and transmits the pulse across a DC power rail, as shownby block 520 (FIG. 5). The luminaire records a first time, correspondingto when the pulse propagates to the luminaire, as shown by block 1220.When the pulse reaches the end of the unterminated transmission line,the pulse is reflected back toward the AC signal generator. Theluminaire records a second time, corresponding to when the reflectedpulse propagates to the luminaire, as shown by block 1230. A differencebetween the first time and the second time is calculated, as shown byblock 1240. The distance of the luminaire to the end of the transmissionline may be calculated, for example, by multiplying the time differenceand the propagation speed of the pulse, and then dividing by two, toaccount for the time of the pulse to propagate from the luminaire to theend of the rail, and then back from the end of the rail to theluminaire.

FIG. 13 shows a transmission line based location method that utilizespulses transmitted along the line 750 rather than, for example,continuous high frequency sine waves. As in the second and thirdembodiment, the line 740 is unterminated causing reflections at the end940. Positions of luminaires 720, 730 along the line 750 may bedetermined by recording the elapsed time between a pulse passing theluminaires 720 while travelling from the generator 710 towards the endof the line 940 and the time when the reflected pulse passes theluminaires 720, 730 again. In particular, the pulse is detected at thefirst luminaire 720 at time t₁ 1310, the pulse is detected at the secondluminaire 730 at time t₂, the reflected pulse is detected at the secondluminaire 730 at time t₃, and the reflected pulse is detected at thefirst luminaire at time t₄. The location of the first luminaire 720along the line 750 may be determined using the difference between t₁ andt₄, while the location of the second luminaire 730 along the line 750may be determined using the difference between t₂ and t₃.

It should be noted that the AC signal generator described in the first,second, third and fourth embodiments may be a stand-alone signaltransmitter in communication with a signal transmitter and/ortransceiver, or may be incorporated within a signal transmitter and/ortransceiver.

DC Rail Communications Channel

As mentioned above, the AC generator may be used to convey control dataor other information with one or more luminaires within the lightingsystem. Like the location signals described above, the communicationschannel uses the DC power distribution rails to convey communicationssignals across the rails. It may be desirable to choose a carrierfrequency for the communication channel sufficiently low that eachluminaire along the rail receives a signal with a substantiallyconsistent signal to noise ratio regardless of the position of theluminaire along the rail. The communications channel may occupy adistinct frequency band from the location signals, for example, usingfrequency division multiplexing. For example, the location channel mayhave a carrier frequency approximately in the 5 MHz range, while thecommunication channel may operate approximately in the 1 MHz range. Ofcourse, there is no objection to using the communication channel over DCpower distribution rails with other channelization techniques used inwired channels, for example, time division multiplexing.

The communications channel conveyed by the DC power distribution railsmay be used to supplant or augment other communications channels used bythe luminaires, for example Zigbee wireless channels. For example, a DCmapper may be in communication with a transceiver sending locationand/or data communications to luminaires, and receiving location and/ordata communications from luminaires.

The luminaire location calculation may be performed by centralizedprocessing, distributed processing, or by a combination of centralizedand distributed processing. For example, luminaires may gather databased on received location signals, and communicate the data to a DCgrid mapper, for example co-located with the signal generator, whereinthe DC grid mapper calculates the luminaire location based upon the datareceived from the luminaires in conjunction with information regardingthe position of the DC grid lines. In another example, the luminairesmay calculate the distance between the luminaires and the source of thelocation signals, and communicate this distance to the DC grid mapper.Similarly, the DC grid mapper may provide the DC grid positioninformation to the luminaires, so the luminaires may calculate theirposition relative to the DC grid. A person having ordinary skill in theart will recognize variations on the luminaire location method andsystem that fall within the scope of this disclosure.

The method and system for identifying and locating luminaires on a DCpower grid may be used, for example, to aid auto-commissioning oflighting systems by automatically obtaining spatial mapping from adeployment within a lighting installation. The luminaire locationinformation provided may then be leveraged by other applications such asscene setting. In addition to first time commissioning, the ID can alsobe used to aid automatic configuration or re-configuration of lightingsystems when, for example, a luminaire is added to or removed from apre-existing installation.

While several inventive embodiments have been described and illustratedherein, those of ordinary skill in the art will readily envision avariety of other means and/or structures for performing the functionand/or obtaining the results and/or one or more of the advantagesdescribed herein, and each of such variations and/or modifications isdeemed to be within the scope of the inventive embodiments describedherein. More generally, those skilled in the art will readily appreciatethat all parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the inventive teachingsis/are used. Those skilled in the art will recognize, or be able toascertain using no more than routine experimentation, many equivalentsto the specific inventive embodiments described herein. It is,therefore, to be understood that the foregoing embodiments are presentedby way of example only and that, within the scope of the appended claimsand equivalents thereto, inventive embodiments may be practicedotherwise than as specifically described and claimed. Inventiveembodiments of the present disclosure are directed to each individualfeature, system, article, material, kit, and/or method described herein.In addition, any combination of two or more such features, systems,articles, materials, kits, and/or methods, if such features, systems,articles, materials, kits, and/or methods are not mutually inconsistent,is included within the inventive scope of the present disclosure.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

It should also be understood that, unless clearly indicated to thecontrary, in any methods claimed herein that include more than one stepor act, the order of the steps or acts of the method is not necessarilylimited to the order in which the steps or acts of the method arerecited.

Also, reference numerals appearing in parentheses in the claims, if any,are provided merely for convenience and should not be construed aslimiting in any way.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” “composed of,” and the like are tobe understood to be open-ended, i.e., to mean including but not limitedto. Only the transitional phrases “consisting of” and “consistingessentially of” shall be closed or semi-closed transitional phrases,respectively.

1. A method for locating a luminaire (250) on a DC grid, the DC gridcomprising a first DC grid power line (240), an AC signal generator(235) switchably connected to the first DC grid power line, and a firstluminaire in electrical communication with the first DC grid power line,the first luminaire disposed along the first DC grid power line at afirst distance from the AC signal generator, the method comprising thesteps of: connecting the AC signal generator to the first DC grid powerline; transmitting, by the AC signal generator, an AC signal along thefirst DC grid power line; receiving the AC signal by the firstluminaire; and calculating the first distance between the AC signalgenerator and the first luminaire, based in part upon the AC signal. 2.The method of claim 1, where the first DC grid power line is terminatedfor the AC signal (701) with a resistance (740) approximating acharacteristic impedance of the first DC grid power line, the methodfurther comprising the steps of: recording, by the first luminaire, afirst phase (721) of the AC signal at the first luminaire; andrecording, by the AC signal generator, a second phase (711) of the ACsignal at the AC signal generator; wherein the step of calculating thefirst distance further comprises measuring a difference between thefirst phase and the second phase.
 3. The method of claim 1, wherein thefirst DC grid power line is unterminated for the AC signal (901), themethod further comprising the steps of: setting the frequency of the ACsignal such that the AC signal forms a standing wave across the first DCgrid power line, the standing wave comprising a maximum amplitude; andrecording, by the first luminaire, a first amplitude (921) of the ACsignal at the first luminaire; wherein the step of calculating the firstdistance further comprises measuring a difference between the firstamplitude and the maximum amplitude.
 4. The method of claim 1, whereinthe first DC grid power line is unterminated for the AC signal, the ACsignal further comprising an amplitude, the method further comprisingthe steps of: sweeping the frequency of the AC signal between a firstfrequency and a second frequency; recording, by the first luminaire, afirst time corresponding to a time the first luminaire initially detectsthe AC signal; and recording, by the first luminaire, a second timecorresponding to a time the first luminaire detects the amplitude of theAC signal corresponding to a null amplitude; wherein the step ofcalculating the first distance further comprises measuring a differencebetween the first time and the second time.
 5. The method of claim 1,wherein the AC signal comprises a pulse signal, the first DC grid powerline is unterminated for the AC signal, the method further comprisingthe steps of: recording, by the first luminaire, a first time (1310)corresponding to a time the first luminaire initially detects the pulsesignal; and recording, by the first luminaire, a second time (1313)corresponding to a time the first luminaire initially detects areflection of the pulse signal; wherein the step of calculating thefirst distance further comprises measuring a difference between thefirst time and the second time.
 6. The method of claim 1, wherein the DCgrid further comprises a second DC grid power line, the AC signalgenerator switchably connected to the second DC grid power line, and asecond luminaire in electrical communication with the second DC gridpower line, the second luminaire disposed along the second DC grid powerline at a second distance from the AC signal generator, the methodfurther comprising the steps of: connecting the AC signal generator tothe second DC grid power line; transmitting, by the AC signal generator,an AC signal along the second DC grid power line; receiving the ACsignal by the second luminaire; and calculating the second distancebetween the AC signal generator and the second luminaire, based in partupon the AC signal.
 7. The method of claim 1, wherein the DC gridfurther comprises a memory, the method further comprising the steps of:storing the first distance in the memory; and communicating the firstdistance to a DC grid mapper.
 8. The method of claim 7, wherein the stepof communicating the first distance to the DC grid mapper furthercomprises the step of transmitting a wireless signal to the DC gridmapper.
 9. The method of claim 7, wherein the memory is disposed withinthe first luminaire, the DC grid mapper is in electrical communicationwith the DC grid, and the step of communicating the first distance to aDC grid mapper further comprises the step of transmitting acommunication signal along the first DC grid power line from the firstluminaire to the DC grid mapper.
 10. The method of claim 1, furthercomprising the steps of: assigning a first identifier to the firstluminaire; and communicating the first identifier between the firstluminaire and the AC signal generator.
 11. The method of claim 10,wherein the step of communicating the first identifier further comprisesthe step of transmitting a wireless signal to the DC grid mapper. 12.The method of claim 10, wherein the DC grid mapper is in electricalcommunication with the DC grid, and wherein the step of communicatingthe first identifier further comprises the step of transmitting acommunication signal along the first DC grid power line from DC gridmapper to the first luminaire.
 13. The method of claim 1, wherein the DCgrid further comprises an EMerge-compliant lighting system.
 14. A systemcomprising: a DC power grid comprising a plurality of DC power lines(240); an AC signal generator (235) switchably connected to at least oneof said plurality of DC grid power lines, said AC signal generatorconfigured to transmit a locator signal along said at least one of theplurality of DC grid power lines; and a plurality of luminaires (250)disposed upon said DC power grid, each of said luminaires comprising areceiver configured to receive said locator signal, logic circuitryconfigured to calculate a distance between said luminaire and said ACsignal generator based on said locator signal, memory configured tostore said distance, and means for transmitting said distance to a roomcontroller (260).
 15. The system of claim 14, wherein said DC gridfurther comprises an EMerge-compliant lighting system.
 16. The system ofclaim 14, wherein said AC signal generator is configured to transmitsaid locator signal within a first frequency band and further configuredto transmit and receive data within a second frequency band.
 17. Thesystem of claim 16, wherein said plurality of luminaires are configuredto receive said locator signal within said first frequency band andfurther configured to receive data within said second frequency band.18. The system of claim 14, wherein said locator signal comprises astanding wave and/or a pulse.
 19. A method comprising the steps of:providing a DC power grid comprising a plurality of DC power lines (240)and a plurality of luminaires (250) disposed upon said plurality of DCpower lines; selecting a first luminaire from said plurality ofluminaires; assigning an ID to said first luminaire; associating saidfirst luminaire with a first DC power line; storing a first coordinateindex comprising the association between said first luminaire and saidfirst DC power line; calculating a position of said first luminaire inrelation to said first DC power line; storing a second coordinate indexcomprising said position of said first luminaire in relation to saidfirst DC power line; and communicating said ID, said first coordinateindex and said second coordinate index to a room controller (260). 20.The method of claim 19, wherein the step of communicating said IDfurther comprises the step of transmitting a wireless signal to saidroom controller.
 21. The method of claim 19, wherein said roomcontroller is in electrical communication with said DC power grid, andthe step of communicating said ID further comprises the step oftransmitting a data signal over said DC power grid.
 22. A method forcontrolling a first luminaire in electrical communication with a firstDC grid power line (240) on a DC grid, said first luminaire (250)comprising a first luminaire data transceiver, said DC grid comprisingsaid first DC grid power line, a grid data transceiver (235) switchablyconnected to said first DC grid power line, and said first luminaire,the method comprising the steps of: connecting the grid data transceiverto the first DC grid power line; transmitting, by the grid datatransceiver, a first data signal along the first DC grid power line; andreceiving the first data signal by the first luminaire data transceiver.23. The method of claim 22, further comprising the steps of:transmitting, by the first luminaire data transceiver, a second datasignal along the first DC grid power line; and receiving the second datasignal by the grid data transceiver.
 24. The method of claim 22, the DCgrid further comprising a second DC grid power line, and a secondluminaire in electrical communication with the second DC grid powerline, said second luminaire comprising a second luminaire datatransceiver, said grid data transceiver switchably connected to saidsecond DC grid power line, the method further comprising the steps of:connecting the grid data transceiver to the second DC grid power line;transmitting, by the grid data transceiver, a third data signal alongthe second DC grid power line; and receiving the third data signal bythe second luminaire data transceiver.
 25. The method of claim 24, theDC grid further comprising the steps of: transmitting, by the secondluminaire data transceiver, a fourth data signal along the first DC gridpower line; and receiving the fourth data signal by the grid datatransceiver.